With 2013 drawing to a close, I thought it only fitting to take a page from Time magazine and look at the most important dinosaurs described by paleontologists in the past year. For 2013, there are four particular new dinosaurs that deserve to examined in detail. One is a serious contender for being a major "first" in the annals of paleontology; the other three dinosaurs, oddly enough, all hail from the same state.
NOTE: I use the term "described", rather than "discovered", to respect the number of years that elapse between paleontologists unearthing a potentially new dinosaur species and presenting it to the public with a name of its own.
DINOSAURS OF THE YEAR
For over 150 years, Archaeopteryx--hailing from Late Jurassic Germany--has been regarded as the first bird.
Now, a creature 10 million years older appears to have a better claim to that title. Aurornis ("dawn bird") inhabited northeastern China roughly 160 million years ago. Like Archaeopteryx, it retained the teeth and long tail of small theropods; however, it was also covered in feathers and had a set of long arms ending in very large hands.
One of the things that marks Aurornis as a more primitive animal than Archaeopteryx are the feathers themselves. While Archaeopteryx had long feathers sprouting from its arms and tail that may have allowed to actually fly, those preserved in the type (i.e. original) specimen of the Aurornis are short and downy, precluding flight in the animal altogether. Instead, they likely served to insulate it, like those of modern kiwis and penguins.
While Aurornis is arguably the greatest dinosaur discovery made in 2013, it should be noted that the discoverer of this dinosaur was not one of the scientists who announced it. Rather, it was a local fossil collector who sold it to the Guizhou Fossil and Geology Park. The collector claimed to have found it in Liaoning, home to other small "dinobirds" from the Late Jurassic such as Epidexipteryx and Anchiornis. Liaoning is also home to forgeries of fossils belonging to these animals, so it may be wise to take the claim that Aurornis was the first bird with a grain of salt.
The past few years have been good ones for tyrannosaur experts, with at least one new genus being described each year. In 2010, the new animal was Bistahieversor from New Mexico. 2011 saw the description of Teratophoneus and Zhuchengtyrannus, from Utah and China respectively. And one of the biggest dinosaur-related news stories last year was the unveiling of Yutyrannus, a primitive, 30-foot long Chinese tyrannosaur discovered with fossilized feathers.
This year, Lythronax ("king of gore") joined this dynasty. Discovered in southern Utah and dating back to 80 million years ago, the back of this monster's skull was broad and its eye sockets faced forward. These features are not common to all large, North American tyrannosaurs from the Late Cretaceous; in fact, the creature in which they are most notable is Tyrannosaurus rex. At 24 feet long and about 3 tons in weight, Lythronax was about half the size of its famous relative and lived about 10 million years earlier. Nonetheless, it was one of the first tyrannosaurs to occupy the niche of top predator in North America and may have been an direct ancestor to the largest and last of their lineage.
Even more so than tyrannosaurs, the ranks of large ceratopsians have swelled significantly since 2010 (with six new genera described that year alone). While some are renamed animals previously belonging to another genus, many are creatures that were completely unknown to science until now. Such is the case with Nasutoceratops ("big-nosed horned face"), which roamed Utah 75 million years ago and is possibly the most bizarre dinosaur described in 2013.
Nasutoceratops was not a particularly advanced member of its family, and at 15 feet in length was only about half the size of Triceratops. What really sets this animal apart from its kin--apart from the deep muzzle for which it is named--are its horns. Ceratopsian horns were long regarded as weapons for goring tyrannosaurs and other potential predators; yet the arrangement of horns in many ceratopsians is inconsistent with this idea. The position of Nasutoceratops' three horns are particularly baffling, as the nasal horn was a tiny stump positioned close to the eyes and the two long brow horns curved inwards. None of these structures were an ideal position for goring anything, and may instead have served to deter potential predators or rivals, to attract members of the opposite sex, or a combination of both.
The third major dinosaur discovery made in Utah this year was of another large meat-eater, this time from the Cedar Mountain Formation. Fifteen million years older than Lythronax, Siats (pronounced "see-atch") belonged to the neovenatorids, an only recently-described family distantly related to Allosaurus. Named after a monster of Ute mythology, the type specimen of this animal is thought to represent an adolescent individual, measuring roughly 30 feet long and weighing 4.5 tons. Adult Siats would have been even bigger, estimated to reach 40 feet in length and another ton or two in weight. These estimates not only make Siats the largest of the neovenatorids, but also one of the largest known carnivorous dinosaurs from North America--on a par with the earlier carcharodontosaur Acrocanthosaurus but lighter and slightly shorter than the largest T. rex.
Beyond its impressive measurements, Siats partially fills a large gap in paleontologists' understanding of North American dinosaur distribution. Allosaurus seems to have been the continent's keystone predator during the Late Jurassic, while different kinds of tyrannosaurs took up that mantle during the Late Cretaceous. Along with Acrocanthosaurus, fossils of Siats demonstrate that this transition was not immediate, and that other theropod families not only filled that role before the tyrannosaurs, but also held on to it for longer than was previously thought.
Acheroraptor- Dromaeosaur similar to Velociraptor that inhabited Montana at the very end of the Cretaceous. It is named after the River Acheron--one of the rivers of the underworld in Greek mythology and an allusion to the bonebed where it was found, the Hell Creek Formation.
Dahalokely- The second abelisaur found in Madagascar, dating back to the mid-Cretaceous (the first, Majungasaurus, lived during the Late Cretaceous). The smallest known member of the group, measuring between nine and fourteen feet in length.
Jianchangosaurus- Very primitive therizinosaur from Early Cretaceous China.
Judiceratops- Large ceratopsian from Late Cretaceous Montana. Earliest known member of the chasmosaurine ceratopsids (the family to which Triceratops belongs) by a few million years.
Trinisaura- Small, Late Cretaceous ornithopod and the fourth dinosaur genus described from Antarctica.
Xinjiangtitan- Super-sized, Mamenchisaurus-like sauropod from mid-Jurassic China.
Ajancingenia- Renaming of the oviraptorosaur "Ingenia", from Late Cretaceous Mongolia. The former name had already been taken by a species of roundworm.
Juratyrant- Late Jurassic tyrannosauroid from England formerly known as "Stokesosaurus langhami."
Sinosaurus- Early Jurassic dilophosaur from China that used to be called "Dilophosaurus sinensis."
Coria, Rodolfo A. et al. "A new ornithopod (Dinosauria; Ornithischia) from Antarctica." ScienceDirect, Apr 2013
Currie, Philip J., David C. Evans, and Derek W. Larson. "A new dromaeosaurid (Dinosauria: Theropoda) with Asian affinities from the latest Cretaceous of North America." Naturwissenschaften, Nov 2013
Dell'Amore, Christine. "New Big-Nosed Horned Dinosaur Found in Utah." National Geographic News, 16 July 2013
Dong, Zhi-Ming et al. "A new gigantic sauropod from the Middle Jurassic of Shanshan, Xinjiang." Global Geology, Sep 2013
Gray, Richard. "Dinosaur that terrorized the Tyrannosaurs found." The Telegraph, 22 Nov 2013
Hone, Dr Dave and Alok Jha. "Lythronax argestes: 'King of Gore' joins T rex family tree." The Guardian, 6 Nov 2013
de Lazaro, Enrico. "Aurornis xui - New Candidate for Oldest Bird." sci-news.com, 10 Jun 2013
Lallanilla, Marc. "New Meat-Eating Dinosaur Fills 95-Million-Year Gap." LiveScience, 26 April 2013
"Lythronax argestes: Scientists discover new ‘King of Gore’ dinosaur species that is ‘great-uncle’ to T-rex." The Independent, 7 Nov 2013
Morelle, Rebecca. "Nasutoceratops: 'Big-nosed, horn-face' dinosaur described." BBC News, 16 July 2013
Pappas, Stephanie. "Newfound Dinosaur, 'Siats Meekerorum', Terrorized Early Tyrannosaurs." The Huffington Post, 22 Nov 2013
Pu, Hanyong et al. "An Unusual Basal Therizinosaur Dinosaur with an Ornithischian Dental Arrangement from Northeastern China." PlosOne, 29 May 2013
Sample, Ian. "Early bird beat Archaeopteryx to worm by 10m years." The Guardian, 29 May 2013
"Scientists discover Judiceratops, New Species of 3-Horned Dinosaur." International Business Times, 3 Jun 2013
Switek, Brian. "Newfound Giant Ruled Before T. Rex." National Geographic News, 22 Nov 2013